Novel nuclear and mitochondrial genetic markers have been developed and described in various species improving our ability to assess patterns of genetic variation within and among species and to reconstruct historical evolutionary events. The results have indicated abundant molecular genetic diversity among South American species, leopards, bobcats and limited variation in North American pumas, tigers, Iberian lynx, and previously documented bottlenecked cheetahs, pumas and lions. Concordant phylogenetic and phylogeographic studies of feline immunodeficiency virus transmission among free-ranging cat populations allows a glimpse of the process of emerging infections in species well suited for discovery of these events. Insight gained from these studies reveals evolved mechanisms for immune and natural defenses against fatal infections and neoplastic diseases. Animal Models for AIDS